Safety during transfusions is a major issue in medical economics. Despite drastic quality control measures, transfusion is still a source of short, mid and long-term morbi-mortality. This can be explained to some extent by changes in the composition of the packed red blood cell (PRBC) supernatant during storage essentially with the appearance of immunologically active compounds possibly involved in organ dysfunction on the one hand and post-transfusion immunomodulation on the other hand. These phenomena impact upon outcomes for cardiac surgery patients.